Efficient Enantioselective Reactions of carbanions α to the Sulfur Functional Groups

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Since 1999, we have studied on the new asymmetric syntheses using organosulfur sompounds. We stucceeded in developing of new diastereoselective reactions of the α-sulfinyl carbanion derived from β-silylethyl sulfoxides, which afforded only a single diastereoisomer in each reaction using aldehydes, and α, β-unsaturated carbonyl compounds. Furthermore, subsequent reaction of the formed enolates with aldehydes also afforded only a single stereoisomer These results strikingly show that these reactions can control the stereochemistry of the four consecutive chiral centers by a chiral sulfoxide.Enantioselective reactions α-sulfenyl carbanions were also studied. Reactions of α-sulfenyl carbanion with various electrophiles in the presence of chiral bisoxazolines. We examined the reactions with aldehydes, ketones, methyl trifluoromethylsulfonate, trimethylsilyl chloride, and carbon dioxide. The reaction of α-sulfenyl carbanion derived from α-stannylbenzyl phenyl sulfide was found that the react … More ion proceeds through a dynamic kinetic resolution pathway. On the other hand, α-sulfenyl carbanion derived from 2-pyridyl sulfide afforded the product having the stereochemistry opposite to the one obtained in the reaction of benzyl phenyl sulfide. This reaction was proved to proceed through a dynamic thermodynamic resolution pathway with inversion of configuration of the intermediate lithium complex.Furthermore, we have studied on the asymmetric reaction caused by the rotational barrier around the C-S bond axis. The 1-sulfinyl-2-formyl and 2-acylnaphthalenes having the 2,4,6-triisopropylphenyl group showed extremely high stereoselectivities in the nucleophilic reactions, Mukaiyama aldol reactions, and reductions. These stereoselectivities are shown to be caused by the rotational barrier around the C-S bond axis by tire ^1H NMR spectra, the X-ray structural analyses and the MO calculations. Elimination of the sulfinyl group from the obtained products afforded chiral alcohol derivatives. Less